Sensors to determine pressure, which may be above or below atmospheric, are frequently used in combination with internal combustion engines, and particularly with mobile internal combustion engines installed in automotive vehicles. Hereinafter, the term "pressure" is intended to mean any pressure other than ambient and the sensor, therefore, is equally suitable to measure pressure below atmospheric, that is, vacuum, or pressure above atmospheric.
Automotive-type pressure sensors require structures which are are small and which are reliable over long operating periods, providing reproducible electrical output signals representative of the pressures being sensed. A typical pressure is induction pipe pressure--or, rather, vacuum--which is to be transduced into electrical signals, to be used to control the operation of the internal combustion (IC) engine. These signals, after suitable transformation, are then applied to control systems where they are further processed to control the operation of the engine.